For many applications, it is desirable to have an on-chip voltage reference that has low impedance from low to high frequencies. This often requires the use of external capacitors to maintain low impedance at high frequencies. One possible implementation is the prior art voltage reference circuit shown in FIG. 1, where a transconductance amplifier 20, with input transconductance gm, is used as an output buffer. An on-chip capacitor 22 can be used to compensate the amplifier 20 so that it will be stable even without the external capacitor 24. Unfortunately, the output impedance at low frequencies, which is essentially given by 1/gm, is not very low. The output impedance can be lowered by increasing gm, at the expense of increasing die area and power. However, it would be difficult to compensate the amplifier 20 with an on-chip capacitor 22 of reasonable size. An alternative approach in CMOS technology is the prior art voltage reference circuit shown in FIG. 2, where a complementary source-follower 26 is used in open loop. Thus, there is no need to worry about stability. But the low-frequency power supply rejection is not very good. It is also more difficult to control the output voltage accurately because of the open-loop approach.